This content is excerpted from the above-named O'Reilly publication, with permission, by agreement with ActionScript.org.

Use WebSpeed Simulator to sidestep the
Bandwidth Profiler's inability to simulate bandwidth
performance when testing through the browser (i.e., real-world
conditions).

When creating a site, you want to know
how long it will take to download at a particular connection speed.
This helps you ensure the best experience for your target audience,
most of whom will have slower connections than those common among
developers. The Flash Bandwidth Profiler is useful for
evaluating the download time for a simple SWF file when simulated in
Test Movie mode. You can access it by using Control?Test
Movie to enter Test Movie mode and then choosing
View?Bandwidth Profiler to open the Bandwidth Profiler
window. However, the Bandwidth Profiler assumes an ideal connection,
so choose a target connection speed somewhat slower than the ideal
speed of your lowest-bandwidth user. For example, choose 28.8 Kbps
instead of 56 Kbps to simulate a typical 56-Kbps modem.

Regardless, the Bandwidth Profiler included with Flash MX 2004
Version 7.0 is too simplistic for more advanced sites. Most
commercially produced Flash sites consist of far more than a single
SWF. Additional assets—such as secondary SWFs, images, MP3
files, video files, remote data, and text files (CSS, XML,
etc.)—are routinely loaded at runtime. Prior to the Flash MX
2004 Version 7.0.1 update, the Bandwidth Profiler did not include
these assets as part of its simulation, so it understated the
download times.

The third-party WebSpeed Simulator (http://www.xat.com) is a useful alternative
to the Bandwidth Profiler. It works by creating a local
bandwidth-limited HTTP server and allows you to:

View the site loading in real time in a web browser on a simulated
bandwidth-limited connection

View a timestamped browser cache, allowing you to review the order in
which files were loaded (plus what is left available in the cache
after your site has been visited)

The WebSpeed simulator is extremely easy to use. However, because the
simulator works as an HTTP server, it cannot emulate secure servers.

Assuming you want to test a site from your local hard drive, click
the application Setup icon in WebSpeed Simulator's
toolbar to bring up the Setup Web Server dialog box, as shown in
Figure 9-1, and specify the location of the site
(i.e., the location of the folder containing your home page, such as
index.html). You may also have to clear the
browser cache depending on your browser settings. (For example, to
clear the cache in Windows Internet Explorer, use
Tools?Internet Options?General?Delete
Temporary Internet Files.)

Figure 9-1. The Setup Web Server dialog box in WebSpeed Simulator

Then, click the Restrict icon and specify your simulated connection
in the Restrict Web Server dialog box, as shown in Figure 9-2. You can also specify whether you want to
preserve the browser cache (i.e., if you visit the same site twice,
content already in the browser cache will load immediately).

Figure 9-2. The Restrict Web Server dialog box in WebSpeed Simulator

Finally, click the Browse icon. The simulator directs the browser to
the folder you specified during setup and acts as a server, limiting
bandwidth as specified in the Restrict Web Server dialog box. As each
item is loaded in the browser, the WebSpeed Simulator displays the
time each file takes to load, the order of loading, and the filesize,
as shown in Figure 9-3.

Figure 9-3. The WebSpeed Simulator results

I keep WebSpeed Simulator running whenever I am working in Flash. It
addresses the failings of the Bandwidth Profiler and provides a clean
interface for easily testing at various bandwidths. Setup is trivial
and you don't need to change your browser settings
or your physical connection to test at different speeds, so it is
very easy to integrate into your normal workflow. It can even
evaluate sites that mix HTML and Flash, whereas the Flash Bandwidth
Profiler works with SWF files only. Experience with using WebSpeed
Simulator confirms it is an accurate simulation—the times
predicted by the simulator are very similar to the actual content
download times.

Final Thoughts

Although WebSpeed Simulator isn't free (it costs
$99, but a 30-day trial is available), it's by far
the easiest environment I've found for testing
bandwidth requirements on any web site design,
particularly for multifile Flash sites.

Keeping it handy during the course of development will prevent
surprises. The ease with which it can be set up allows you to even,
say, demo a site under simulated web conditions to a client using
your laptop. This comes in handy when helping your client understand
bandwidth considerations when making design decisions. It even works
for Flash applications that load a lot of dynamic data, so it is
invaluable to RIA developers and motion graphics designers
alike.